The present invention relates in general to heating of the passenger cabin in motor vehicles, and, more specifically, to operation of an auxiliary heater during times that an internal combustion engine of the vehicle is off.
In order to provide passenger comfort and to maintain the windows free of ice and condensation, motor vehicles are provided with heaters to provide heat to the passenger cabin. The primary source of heat is usually waste heat from operating an internal combustion engine, wherein liquid coolant circulating through the engine is passed through a heater core which exchanges waste heat into the passenger cabin. In order to precondition the cabin and clear the windows during cold weather, a remote start capability has been provided to allow the user to start the internal combustion engine before arriving at or entering the vehicle. However, running the internal combustion engine only for supplying interior heat is not the most energy-efficient way to heat the cabin. Furthermore, prolonged idling of an engine while a vehicle is parked is sometimes prohibited by law.
As a result, auxiliary heaters (also called parking heaters) have come to be used that operate independently of the combustion engine using either combustible fuel and/or stored electricity as an energy source. Typically, the auxiliary heater is coupled to the engine coolant circuit in order to share the coolant for distributing the generated heat. Coolant may sometimes be circulated using an auxiliary pump (not depending upon engine operation). Coolant is heated in the auxiliary heater and flows to a heater core where it releases the heat into an air flow to the passenger cabin. An example of a parking heater utilizing the fuel supply of the combustion engine is the Thermo Top Evo parking heater from Webasto Thermal and Comfort SE of Gilching, Germany.
The parking heater function has typically been activated by a manual switch (a Human Machine Interface, or HMI, setting) in the vehicle interior, by remote control, or by use of a preprogrammed timer. Conventional parking heater controls, however, have not been well adapted to certain usage patterns of particular users. Furthermore, limitations of conventional user interfaces have resulted in customer dissatisfaction.
More specifically, some drivers (e.g., delivery drivers) may operate a vehicle by making frequent stops and starts along a route. So that the vehicle and its contents remain secure while the driver is away from the vehicle to deliver a package inside a building, for example, the driver shuts off the ignition switch and removes the ignition key. Even if the ignition key is not removed, the delivery driver may be required by regulations to shut down the engine while being parked to deliver a package. If the driver desires to maintain cabin heating while away, it has been necessary to perform a control sequence using either interior control switches or a remote control to activate the parking heater. Thus, it becomes cumbersome for the driver to maintain cabin heating during frequent stops.
Similarly, any driver who arrives early at their destination may want to remain in the parked vehicle for a while without exiting. It may also be desired (or required) to shut down the engine during their wait time. The conventional ignition switch includes an Accessory position which can be used to shut down the engine while continuing to use certain electrical accessories in the vehicle such as a radio. But since the engine is shut down, only the air blower function of the climate control system is usually available with the ignition control in the Accessory position. If the driver wants to obtain interior heating as they wait, convention control interfaces have required manual control actions for every occurrence. It would be desirable to allow the driver to shut down the engine while continuing to obtain parking heat without always have having to initiate such a function.
Operation of the parking heater normally depends on certain conditions being present. For example, the heater should only operate if there is at least a threshold amount of fuel in the fuel tank and the ambient temperature is below a certain temperature. Electrical energy is used even for a fuel-based auxiliary heater in order to run an auxiliary coolant pump. Therefore, heater operation may also depend on a battery state of charge being greater than a predetermined minimum Proper combustion in a fuel-based heater may depend on maintaining a level orientation of the combustion unit, so that operation cannot be permitted with the vehicle on an extreme grade. In addition, the manufacturer typically defines a maximum duration for which the parking heater may operate without the combustion engine being restarted. In view of this conditional operation, a user's attempt with a wireless remote to preheat the cabin with the auxiliary heater function might be unsuccessful due to insufficient fuel, a high ambient temperature, being parked on an excessive grade, or other reasons. However, since the user may not be aware of the potential causes for a failed operation, they may be very dissatisfied when they discover that the cabin has not been preheated and may assume that their vehicle is defective.
In connection with preprogrammed activation times for the parking heater, difficulties may arise when a particular vehicle is driven by more than one person. For example, one user may configure an automatic pre-heating operation for a certain day and time, but then the vehicle is driven by a second user on the preprogrammed day without knowledge of the preprogrammed settings of the auxiliary heater. Unexpected heater operation can thus occur, which may be disconcerting for the second user. Furthermore, byproducts of combustion from the parking heater may be unintentionally released in an enclosed space since the second user could not anticipate the action of the heater. Moreover, since the second user may not desire to have an automatic operation at the preprogrammed time there may be unwant battery drain and fuel use.